Attachment of optical fibers to a connector body

ABSTRACT

An apparatus connectible to an instrument comprising an optical fiber for conducting light along its length and a connector body for use in coupling the optical fiber to the instrument. The connector body defines an enclosure having an entrance passage leading into the enclosure and an exit passage leading from the enclosure. The optical fiber extends through the entrance passage into the interior of the enclosure and into the exit passage. The optical fiber has an enlarged end portion which cooperates with the exit passage to retain the end portion in the exit passage.

BACKGROUND OF THE INVENTION

Fiber optics are used in catheters and probes for the purpose oftransmitting light into and receiving light from internal regions of thebody. Because a catheter or probe must be sized to be received within avein or artery, the fiber optics used within such an apparatus must alsobe of very small diameter.

For example, a catheter or probe may include an elongated tube havingproximal and distal openings and fiber optic means in the form of one ormore fiber optic light conductors in the passage and extending throughthe proximal opening to provide a proximal section of the fiber opticmeans outside of the tube. The fiber optic means is coupled to aconnector body, and the connector body is received within a cavity of areceptacle which optically couples the catheter to an instrument. Thereceptacle may be considered as part of the instrument. The instrumentmay, for example, provide a source of light for transmission through thecatheter and the necessary equipment to process a light signal receivedfrom the catheter.

One problem with this construction is the mounting of the fine fiberoptic light conductors on the connector body. The fiber optic lightconductors, each of which comprises one or more optical fibers, must belocated with respect to the connector body with great precision andsecurely retained in position. This is necessary so that light can betransmitted efficiently between the instrument and the catheter.Locating the fiber optic light conductor on the connector body withprecision is difficult because of the small diameter of the opticalfibers.

It is also important to assure that the connector body is tightly seatedwithin the receptacle. If this is not done, losses will occur at theinterface. Moreover, the connector body and receptacle must cooperatewith each other to precisely position the connector body within thereceptacle to maximize the optical coupling between the connector bodyand the receptacle.

SUMMARY OF THE INVENTION

This invention solves the problems noted above. With this invention, thefine, small diameter fiber optic light conductors are securely andprecisely mounted on the connector body. This is accomplished in a waywhich facilitates assembly and minimizes production cost. Although thesefeatures are particularly applicable to a catheter or probe which issized to be received with a vein or artery, they are also applicable tothe mounting of a fiber optic light conductor on a connector body foruse with various other devices.

The connector body of this invention can advantageously include wallmeans defining an enclosure and an entrance passage and an exit passagein the wall means. The fiber optic means extends through the entrancepassage into the enclosure and into the exit passage. The fiber opticmeans has a proximal end within or closely adjacent the exit passage.Because the exit passage can be precisely located, the end of the fiberoptic means is correspondingly accurately located and it can beoptically coupled to a selected part of the receptacle.

The fiber optic means is retained in the exit passage. With thisinvention, the retaining means includes a shoulder in the exit passageand an enlargement on the fiber optic means adjacent the proximal endthereof which cooperates with the shoulder to at least assist inretaining the fiber optic means in the exit passage. An adhesive mayalso be used.

The fiber optic means is preferably of the type which can be radiallyenlarged by heating. This permits the enlargement to be formed by theapplication of heat.

To facilitate insertion of the end of the fiber optic means into theexit passage, a tapered groove is provided in the wall of the enclosurewhich leads to, and narrows toward, the exit passage. To prevent theentrance of ambient light into the enclosure at this region, the taperedgroove preferably does not extend completely through the wall.

More specifically, the exit passage has an entrance section on one sideof the shoulder and an exit section on the other side of the shoulder,and the exit section has first and second surface portions. Theenlargement is radially, compressively engaged by the first surfaceportion, and material is displaced from at least one of the firstsurface portion and the enlargement to the region between the secondsurface portion and the enlargement. Preferably, material from theenlargement is displaced. Thus, the first surface portion provides forthe compressive engagement and the second surface portion allows for thedisplacement of material resulting from the compressive engagement. Thecompressive engagement tightly retains the end portion of the fiberoptic means within the exit passage so that any adhesive being used cancure, and there is no need for a separate fixture to hold thesecomponents in position during curing of the adhesive. Preferably, thefirst surface portion includes at least three generally flat surfacesarranged circumferentially within the exit passage. Although curvedsurfaces could be used, they tend to present sharp corners for theenlargement, and for that reason, curved surfaces are not preferred. Ina preferred construction, the flat surfaces are set back from theexterior opening of the exit passage so that, in molding the connectorbody, there will be no flash at the exterior opening.

The fiber optic means may include one or more fiber optic lightconductors, and one of the exit passages is provided for each of thefiber optic light conductors. Each of the fiber optic light conductorsmay include one or more optical fibers. The fiber optic light conductorsmay form a portion of a probe or catheter.

In carrying out the method of this invention, a fiber optic lightconductor is inserted through the exit passage so that it has an endportion on the exit side of the passage. The end portion of the fiberoptic light conductor is then radially enlarged, and this is preferablycarried out by heating as described above. The radially enlarged endportion is then forced back into the exit section of the passage tocompressively engage the enlarged end portion with the first surfaceportion and to displace material from one or both of the first surfaceportion of the wall and the enlarged end portion as described above.

The invention, together with additional features and advantages thereof,may best be understood by reference to the following description takenin connection with the accompanying illustrative drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partially schematic, isometric view illustrating anapparatus constructed in accordance with the teachings of thisinvention.

FIG. 1a is a fragmentary, isometric view of a distal end portion of acatheter.

FIGS. 2 and 2a are fragmentary, top plan views of the receptacle andconnector body, with the connector body partially and fully insertedinto the receptacle, respectively.

FIGS. 3 and 3a are fragmentary sectional views taken along lines 3--3and 3a--3a of FIGS. 2 and 2a, respectively.

FIG. 4 is an exploded isometric view of the connector body with thelight conductors removed.

FIG. 5 is an enlarged, fragmentary sectional view of a portion of theconnector body which includes the exit passage.

FIG. 6 is an enlarged, fragmentary sectional view taken generally alongline 6--6 of FIG. 4.

FIGS. 6a-6c are fragmentary, sectional views similar to FIG. 6illustrating a preferred method of retaining the light conductor in theexit passage.

FIG. 7 is an enlarged elevational view taken generally along line 7--7of FIG. 6.

FIGS. 7a and 7b are views taken generally along lines 7a--7a and 7b--7b,respectively, of FIG. 6c.

FIGS. 8 and 8a are enlarged fragmentary sectional views taken generallyalong line 8--8 of FIG. 4 and illustrating the entrance passage emptyand with the light conductors installed therein, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a catheter 11 which can be releasably coupled to aninstrument 13 using a connector body 15 and a receptacle 17. Thereceptacle 17 may be considered as part of the instrument 13. Althoughthe features of this invention are particularly adapted for use with acatheter, the invention is not limited to use with a catheter, and theparticular catheter shown is purely illustrative.

The catheter 11 includes a tube 19 sized to be received within a vein oran artery of a patient and having proximal and distal ends and aplurality of lumens or passages, including passages 21 and 23 extendinglongitudinally through it. The passage 21 has a distal opening 25 (FIG.1a) and a proximal opening 27 (FIG. 1). A balloon 29 is provided on thetube 19 adjacent the distal tip of the catheter.

The catheter 11 also includes fiber optic means 31 extending completelythrough the passage 21 of the tube 19 from the distal opening 25 throughthe proximal opening 27 to provide a proximal section 33 of the fiberoptic means outside of the tube. Of course, other tubing incommunication with the other passages of the tube 19 can also exit atthe proximal opening 27. Although various constructions are possible, inthe embodiment illustrated, the fiber optic means 31 includes fiberoptic light conductors 35 and 37 for conducting light to the distalopening 25 and for conducting a light signal away from the distalopening 25, respectively. The distal ends of the light conductors aretightly retained within the passage 21, which is of larger cross sectionthan the two light conductors, by a spacer 32 (FIG. 1a). A catheter ofthis type can be used to measure the oxygen saturation of blood bydetermining its color absorption characteristics in accordance withknown techniques. To make this determination, the catheter 11 isinserted into the heart of the patient to place the distal opening 25 inthe pulmonary artery.

The proximal section 33 of the fiber optic means 31 is coupled to theconnector body 15, and the details of the connector body are shown inFIGS. 2-8a. The connector body 15 has wall means which define anenclosure, and the wall means includes a circumscribing peripheral wall39, a floor 41 and a cover 43 (FIG. 4). Supporting feet 44 (FIGS. 3 and3a) extend downwardly from the floor 41. The peripheral wall 39 includesopposed side walls 45 an end wall or face 47 and an end wall 49. Theperipheral wall 39 extends perpendicular to the floor 41 and has a ledge51 and a lip 53 projecting from the ledge. The cover 43 is receivablewithin the lip 53 and onto the ledge 51 with a snap fit to releasablyretain the cover in position.

The face 47 includes identical face sections 55 (FIGS. 2 and 4)separated by a tapered gap 57 which narrows as it extends inwardly ofthe enclosure and which is defined by a channel section 59. The face 47also has inclined corner sections 61 which join the sections 55 to theside walls 45, respectively.

The face sections 55 have identical recesses 63, respectively, whichopen into the gap 57 (FIGS. 3, 3a and 4). The face sections 55 are flatand coplanar, except for the recesses 63. Each of the recesses 63 ispartially defined by an inclined cam follower surface 65. The other sidesurfaces of each of the recesses 63 are also inclined and they terminateinwardly in a flat bottom surface.

Each of the side walls 45 has a recess or groove 67 in its exteriorsurface, and each of the grooves has a longitudinal axis which extendsperpendicular to the longitudinal axis of the associated side wall. Eachof the grooves 67 is identical and is partially defined by a inclinedcam surface 69 along the forward or leading side of the groove. The camsurfaces 69 are used as described more fully hereinbelow for connectingthe connector body 15 to the receptacle 17.

The connector body 15 can be of two-piece, molded plastic constructionas shown in FIG. 4. The cover 43 is configured to mate with and closethe opening at the upper end of the construction formed by theperipheral wall 39 and the floor 41. The floor 41 may have a centralaperture 71.

The end wall 49 has an entrance passage 73, and each of the facesections 55 has an identical exit passage 75. Because the exit passages75 are identical, only one of them is described in detail herein. Asshown in FIG. 8, the end wall 49 has a pair of legs 77 which projectinwardly into the enclosure and define shoulders 79 on opposite sides ofthe entrance passage 73.

The entrance passage 73 cooperates with the proximal section 33 of thefiber optic means 31 as shown in FIG. 8a. Specifically, the proximalsection 33 includes a sheet of shrink tubing 81 and a shorter section ofshrink tubing 83 shrunk over and glued to the tubing 81. The tubing 83forms an annular shoulder 85 which engages the shoulders 79 as shown toprovide strain relief.

Thus, the proximal section 33 of the fiber optic means 31 passes throughthe entrance passage 73 and into the interior of the enclosure. As shownin FIGS. 2 and 2a, the light conductors 35 and 37 extend beyond the endof a sheath 87 in which they are encased, and an excess length of bothof the light conductors is provided within the enclosure. In thisembodiment, each of the light conductors 35 and 37 is in the form of afine, small diameter optical fiber. The light conductors 35 and 37extend into the exit passages 75, respectively, and they are retained inthese exit passages with their ends flush with the outer surface 88(FIG. 6c) of the associated face sections 55.

To facilitate insertion of the light conductors 35 and 37 into theassociated exit passage 75, tapered lead-in grooves 89 are provided onthe interior surfaces of the face sections 55 as shown in FIGS. 4 and 5.Each of the lead-in grooves 89 is identical and extends from the ledge51 to the associated exit passage 75, and it progressively narrows as itextends toward such exit passage. In the embodiment illustrated, each ofthe lead-in grooves 89 tapers linearly, except for a step 91 closelyadjacent the exit passage 75. With this construction, the lightconductor 37 can be easily inserted into the wide end of the lead-ingroove 89 adjacent the ledge 51 and guided toward, and into, the exitpassage 75.

A preferred construction of the exit passage 75 is shown in FIGS. 6 and7. The exit passage 75 has an entrance section 93 of reduced crosssection, an exit section 95 of enlarged cross section, a shoulder 97between these sections, and flat surfaces or surface portions 99 andcurved surfaces or surface portions 101 arranged circumferentially inthe exit section of the passage. The flat surfaces 99 are set backslightly from the exterior surface 88 of the face section 55 at whichthe exit passage 75 opens. If desired, a region of the flat surfaces 99adjacent to the outer surface 88 may be inclined radially inwardly asthey extend toward the outer surface 88.

The surfaces 99 and 101 are arranged circumferentially in the exitsection 95. Although various constructions are possible, in theembodiment illustrated, there are three identical flat surfaces 99 andthey are spaced apart 120 degrees. Each of the curved surfaces 101 isidentical and comprises a segment of a cylinder. One of the curvedsurfaces 101 lies circumferentially between adjacent flat surfaces 99.

The flat surfaces 99 are closer together radially than the surfaces 101.For example, the flat surfaces 99 may be sized and arranged to receive amember of 0.0135 inch diameter, and the curved surfaces 101 may besegments of a cylinder having a diameter of 0.016 inch.

To attach the light conductor 37 to the face section 55, the lightconductor 37 is inserted into the exit passage 75 using the lead-ingroove 89 and through the exit passage as shown in FIG. 6a. Accordingly,the light conductor 37 has an end portion 105 on the exit section sideof the exit passage 75. Next, the end portion 105 is radially enlarged.Although the radial enlarging of the light conductor 37 can be carriedout in different ways, this is preferably accomplished by using a lightconductor of the type which radially enlarges in response to beingheated. For example, an optical fiber comprising an acrylic core and afluoropolymer sheath will radially expand and axially contract inresponse to heating. Preferably, the end portion 105 is heated toradially enlarge the end portion to form an enlargement 107 (FIG. 6b) ofthe desired cross-sectional area which may be frustoconical with themajor diameter at the end of the light conductor. For example, a lightconductor having a diameter of 0.010 inch can be enlarged to a diameterof about 0.015 inch by exposing the end portion 105 to a temperature ofabout 550 degrees Fahrenheit and continuing that exposure for about 8seconds.

Next, the enlargement 107 is forced into the exit section 95 of the exitpassage 75 to compressively engage the enlargement with the flatsurfaces 99 as shown in FIGS. 6c, 7a and 7b. Preferably, the enlargement107 is pushed back into the exit section 95. As shown in FIG. 6c, at thecompletion of this step, a proximal end 109 of the light conductor 37 isflush with the outer surface 88 and is therefor at a known location onthe surface 88.

The enlargement 107 is somewhat deformable and its diameter is greaterthan the diameter than can be accepted by the flat surfaces 99.Accordingly, the forcing of the enlargement 107 between the flatsurfaces 99 displaces material from the enlargement 107circumferentially to regions 111 (FIG. 7a) between the enlargement 107and the curved surfaces 101. As shown in FIG. 7a, there are threeregions 111, each of which is in the form of a radial gap. Accordingly,the enlargement 107 is frictionally retained in the exit section 95 bythe flat surfaces 99 and, in addition, the enlargement 107 at itsjuncture with the non-enlarged portion of the light conductor 37 definesa shoulder which engages the shoulder 97 to inhibit withdrawal of thelight conductor through the entrance section 93. Preferably, a suitableadhesive is applied to the enlargement 107 and/or to the surfaces of theexit passage 75 prior to forcing the enlargement 107 back into the exitsection 95. Accordingly, the frictional retention of the enlargement 107by the flat surfaces 99 serves, in effect, as a fixture to hold thelight conductor 37 within the exit passage 75 while the adhesive cures.Inclining regions of the flat surfaces 99 adjacent the outer surface 88radially inwardly as they extend toward the surface 88 helps to lock theenlargement 107 in the exit passage 75. The flat surfaces 99 alsoaccurately center the light conductors.

The receptacle 17 (FIGS. 1-3a) comprises a body 113 and a cover 115mounted on the body for slidable movement longitudinally of the body.The body 113, which may be molded from a suitable plastic material,comprises a floor 117, side walls 119 and a face 121 (FIGS. 2-3)cooperating to define a cavity 123 sized to receive the connector body15. The face 121 is flat and planar, except for a central wedge-shapedprojection 125 adapted to be received within the gap 57 and for camsurfaces 127 adapted to cooperate with the cam follower surfaces 65,respectively. Light conductors 129 extend within the receptacle 17 andhave their ends mounted in and flush with the face 121 at locations 131,respectively. The locations 131 are arranged to be in confronting andsubstantially aligned relationship with the exit passages 75,respectively, when the connector body 15 is received within the cavity123.

The floor 117 has a slot 133 to separate the adjacent portions of thereceptacle 17 into resilient sections 135 (FIG. 1). A projection 137 ismounted on and carried by each of the side walls 119. The resilientsections 135 and the projections 137 form biasing means or a biasingmember capable of exerting inward force on the connector body 15. Ofcourse, the biasing means can be formed in other ways.

To attach the connector body 15 to the receptacle 17, the connector bodyis advanced into the cavity 123 and slid in a direction to bring thefaces 47 and 121 closer together. During this sliding movement, the feet44 of the connector body 15 slide along the floor 117 of the receptacle17, and the inner surfaces of the side walls 119, the floor 117, theprojection 125 and the confronting surfaces of the connector body 15form guide means for guiding the connector body along a path in thecavity 123 to place the faces 47 and 121 in confronting relationship andto bring the proximal ends 109 of the light conductors 35 and 37 intoengagement with the locations 131. As the connector body 15 is advancedinto the cavity 123, the side walls 45 of the connector body 15 engagethe projections 137 and urge the resilient sections 135 resiliently awayfrom each other. When the proximal ends 109 are nearly in engagementwith the locations 131 as shown in FIGS. 2 and 3, the projections 137engage the cam surfaces 69 and urge the connector body 15 farther intothe cavity 123 to place the faces 47 and 121 into engagement and toplace the proximal ends 109 into engagement and substantial axialalignment with the locations 131. The projections 137 cooperate with thegroove 67 to retain the connector body 15 in the cavity 123 of thereceptacle 17.

In the position shown in FIGS. 2 and 3, the cam follower surfaces 65 arenearly in engagement with the cam surfaces 127. The final advancingmotion of the connector body 15 into the cavity 123 causes the camfollower surfaces 65 to engage the cam surfaces 127 to lift the forwardend of the connector body 15, and in particular the forward foot 44, offof the floor 117 as shown in FIG. 3a. This elevation of the forward endof the connector body 15 accurately positions the exit passages 75 andbrings them into correct alignment with the locations 131. The camsurfaces 127 and the cam follower surfaces 65 also cooperate to assistin holding the connector body 15 in the desired orientation within thecavity 123.

The cam surfaces 127 and the cam follower surfaces 65 form a portion ofthe guiding means for guiding the connector body 15 into the properlocation within the cavity 123. Thus, the path along which the connectorbody 15 moves extends in a first direction, which is generally along thelongitudinal axis of the body 113, until the cam follower surfaces 65contact the cam surfaces 127 and then in a second direction along thecam surfaces 127. This latter portion of movement of the connector body15 occurs when the faces 47 and 121 are closely adjacent and may beunder the influence of the biasing action of the receptacle 17 and thecooperation between the projections 137 and the cam surfaces 69.

The cooperation between the projections 137 and the cam surfaces 69automatically draws the connector body 15 completely into the correctseated position within the cavity 123. This final movement isaccompanied by an audible "click" to inform the operator of the correctseating. The force provided assures that the optical portions, i.e., theproximal ends 109 and the locations 131, will be in contact and inproper registry.

In use, the instrument 13 may provide light through one of the lightconductors 129 to the light conductor 35, and this light is transmittedthrough the interface at the faces 47 and 121 to the light conductor 35which transmits it to the distal opening 25. Assuming that the catheter11 is correctly positioned within a vein or artery within the patient,the light at the distal opening from the light conductor 35 is directedagainst the patient's blood. The blood reflects light into the lightconductor 37, and the reflected light forms a signal having acharacteristic related to the absorption characteristics of the blood.The light signal is transmitted through the light conductor 37 and intothe other of the light conductors 129. The light signal is converted toan electrical signal within the receptacle 17 and transmitted to theinstrument 13 for processing in accordance with known techniques todetermine the oxygen saturation of the blood.

Although an exemplary embodiment of the invention has been shown anddescribed, many changes, modifications and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

We claim:
 1. An apparatus connectible to an instrument, said apparatuscomprising:fiber optic means for conducting light along its length; aconnector body for use in coupling the fiber optic means to theinstrument; said connector body including wall means defining anenclosure and an entrance passage and an exit passage in the wall means,the fiber optic means extending through the entrance passage into theenclosure and into the exit passage, said fiber optic means having aproximal end within or closely adjacent the exit passage whereby saidproximal end of the fiber optic means can be optically coupled to aselected part of the instrument; means for retaining the fiber opticmeans in said exit passage; said retaining means including a shoulder insaid exit passage and an enlargement on said fiber optic means adjacentthe proximal end thereof which cooperates with said shoulder to at leastassist in retaining the fiber optic means in said exit passage; and saidexit passage having an entrance section on one side of said shoulder andan exit section extending beyond said shoulder on the other side of saidshoulder and the exit section having first and second surface portions,said enlargement being radially compressively engaged by the firstsurface portion and material being displaced from at least one of thefirst surface portion and the enlargement to the region between thesecond surface portion and the enlargement.
 2. An apparatus as definedin claim 1 wherein said fiber optic means can be radially enlarged byheating and said enlargement includes a portion of the fiber optic meansenlarged by heating.
 3. An apparatus as defined in claim 1 wherein theenlargement is spaced radially from the second surface portion and saidfirst and second surface portions are circumferentially arranged.
 4. Anapparatus as defined in claim 1 wherein said first surface portionincludes at least three generally flat surfaces arrangedcircumferentially within said exit passage.
 5. An apparatus as definedin claim 4 wherein said exit passage opens at the exterior of saidenclosure and said flat surfaces are set back from said exterior openingof the exit passage, said fiber optic means can be radially enlarged byheating and said enlargement includes a portion of the fiber optic meansenlarged by heating.
 6. An apparatus as defined in claim 4 wherein theexit passage has an outlet and a region of each of said flat surfacesadjacent the outlet is inclined radially inwardly as it extends towardthe outlet of the exit passage.
 7. An apparatus as defined in claim 1including a tapered groove in said wall means and within said enclosureleading to and narrowing toward the exit passage to facilitate insertionof the fiber optic means into said exit passage, said groove extendinggenerally transversely of the exit passage.
 8. An apparatus as definedin claim 1 including an elongated tube sized to be received within avein or artery and having proximal and distal ends and at least oneelongated passage with proximal and distal openings, said fiber opticmeans being partially in said passage and being capable of conductinglight to said distal opening and from said distal opening, said fiberoptic means extending through said proximal opening to provide aproximal section of said fiber optic means outside of said tube, atleast a portion of the proximal section extending through said entrancepassage and into said enclosure.
 9. An apparatus as defined in claim 8wherein said fiber optic means includes first and second fiber opticlight conductors, said exit passage is a first exit passage and saidenclosure has a second exit passage, and said second fiber optic lightconductor is received in said second exit passage.
 10. A method ofinstalling a fiber optic light conductor in a passage through a wall,said method comprising:providing a passage with an entrance section ofreduced cross section, an exit section of enlarged cross section, ashoulder between said entrance and said exit sections, and first andsecond surface portions arranged circumferentially in the exit sectionof the passage; inserting the fiber optic light conductor through thepassage so that the fiber optic light conductor has an end portion onthe exit section side of the passage; radially enlarging the end portionof the fiber optic light conductor; and forcing the radially enlargedend portion into the exit section of the passage to compressively engagethe enlarged end portion with the first surface portion and to displacesome material from at least one of the first surface portion and theenlarged end portion circumferentially to the region between the secondsurface portion and the enlarged end portion and to bring the enlargedend portion into proximity to the shoulder whereby the end portion isfrictionally retained in the exit passage and the enlarged end portioncan inhibit withdrawal of the fiber optic light conductor through theentrance section of the passage.
 11. A method as defined in claim 10wherein the wall has a tapered groove on the entrance section sidethereof leading to and narrowing toward the entrance section and saidstep of inserting includes passing the end portion of the fiber opticlight conductor through at least a portion of the tapered groove andinto the entrance section of the passage.
 12. A method as defined inclaim 10 wherein the fiber optic light conductor is of the type whichradially expands when heated and said step of radially enlargingincludes heating the end portion of the fiber optic light conductor toradially enlarge the end portion to the extent desired.
 13. A method asdefined in claim 10 wherein the enlarged end portion is at leastsomewhat deformable and is radially compressively loaded by said firstsurface portion to displace some of the material thereof to the regionbetween the second surface portion and the enlarged end portion.
 14. Amethod as defined in claim 10 wherein said step of providing includesproviding a passage in which the first surface portion comprises atleast three generally flat surfaces arranged at approximately 120degrees with respect to each other and with the second surface portioncomprising three surfaces located circumferentially between adjacentflat surfaces.
 15. A method as defined in claim 10 wherein said endportion terminates in an end, said wall has a surface on and contiguousthe exit section side of the passage and said step of forcing includespushing the fiber optic light conductor into said exit section untilsaid end of the fiber optic light conductor is substantially flush withsaid surface of the wall.
 16. A method as defined in claim 10 includingapplying an adhesive to at least one of the enlarged end portion and thesurface of the exit section and using the frictional retention of theenlarged end portion in the exit section as a fixture to hold theenlarged end portion in the exit section while the adhesive cures.